Getting rid of automatic terrain cut-out under protruding building feature??

[tradesof]

I have diligently looked through the help topics, knowledge base and the forum and haven't found the answer. I am a new user, so this may be such a simple thing that it doesn't warrant a special mention.

 

In HD Pro 2018 I am drawing a chimney feature that protrudes outside the house, but does not reach the ground. The program automatically cuts the terrain under it - even if I designate the chimney "room" as a balcony. As the chimney is framed just like the house, I have used exterior walls to shape it.

 

So how do I eliminate the automatic terrain hole under the feature like this? 

 

Image attached. Thank you in advance! 

[tradesof]

Great - thank you so much, Eric!

I've added the signature, too.